Reinforced-concrete floor construction.



A. E. LINDAU.

REINPOROEO OONORETE FLOOR OONSTROOTION. APPLICATION FILED APR. 14,1911.` wglgf?. Patented Jan. 14, 1913.

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A. E. mmm. REINFOROBD CONCRETE FLOOR CONSTRUCTION.

APCPLIUATION FILED APR. 14, 1911.

Patented Jan. 14, 1913.

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A. E. LINDAU.

REINFOROBD CONCRETE FLOOR CONSTRUCTION. APPLIUATION FILED 111211.14,1911i 1,050,477. Patented Jan. 14,1913.

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UNTTED sTATEs PATENT oEEroE.

ALIBED E. 'LINDA-U, ST. LOUIS, MISSOURI, ASSIGNOB T0 CORRUGATED BABCOMPANY, OF ST. LOUIS, MISSOURI, A -COZR'POIBA'IIOll' 0F MISSOURI.

BEINFORCED-CONCRETE FLOOR CONSTRUCTION.

Specioation of Letters Patent. Application led April 14, 14911. v SerialNo. 621,072.

To all whom t may concerne Y Be. it known that LALFRED E. LINDAU, a anda resident of the city of St. Louis and State of Missouri, have inventeda new and useful Improvement in Reinforced-Concrete Floor Construction,of which the following 1s a specification.A

My invent-ion relates to a new system of arrangement of reinforcing rodsin concrete floors of the type in which a flat slab of concrete ofsubstantially uniformthickness is supported directly upon the columncaps, without the .intervention of glrders.

Investigation has shown that the dlstribution of tension stresses ingirderless reinforced concrete doors is such that present methods ofreinforcement do not adequately cover the, tension regions.Particularlyis this true in the upper surface of floor slabs.tersecting'- the co umns, or what may be temieds longthe edges of theiioor panel. Itis also necessary .tect the tension re adjacent to the coto more' carefully pro- `on immediately over and umns. Heretofore it hasbeen a general practice to place layers of reinforcin bars 1n the bottomcentral region of the s ab, said bars extending from the :bottom centralregion of the slab in several .directions up into, or near the uppersurface of the slab at its edges, and in some cases to add to these slabbars one or more layers of additional bars, usually straight, ar-

ran in the top of the slab. The result isiirst of all,.to pile u so manylayers of bars'in-the topof, the s ab at its edges as to bring the-center of gravity of the reinforcement'at these points nearer theneutral axis ofthe slab, making this reinforcement proportionatel lesseffective, and in the second place t e bent upbars usually dip down fromthe top to the bottom surface of the slab so near the columns as toleave a large portion of the tension region in the top of the slab abovethe columns unpro# tected. I have devised a system or method ofreinforcing door slabs of this type, that is, that in whlch girdersacross the columns are dispensed with, which will more adequately takecare of the stresses and with a less amount of metal reinforcement, thanis possible with the systems in general use.

My improvements consist in placing the bar's parallel to the rows ofcolumns or view,

edges of the panels and crossing the anels in two directions only, atright ang es to each other, and in the detail arrangement ofreinforcement as is shown in the drawings accompanying thisspecification, and forming a part thereof.

My improvements are not restricted to girderless concrete floors but areapplicable to the arrangement of the reinforcing rods in tile-concreteor composite doors, and floors divided into sections or panels bygirders connecting the columns.

Patented Jan. 14,1913.

In the drawings, 1n which like parts are i designated by like characters.wherever they occur,.-F1gure 1- is a plan view .of the rcinforcement ina center panel of a at slab of an adjacent panel 5 thereinforcement 1nthe top of the slab being shown in full lines and that in bottom of theslab in dotted lines; Fig. 2 is a similar view of a .wall

panel of a flat slab floor embodying my in- 4floor embodying myinvention, showing part v vention;. Fig. 3 is a transverse sectionthrough a center panel along the line 3 3 in Fig. 1; Fig. 4 is atransverse ,sect-ion through a wall panel along the line 4-4 in Fig. 2;vand Fig. 5 is a diagrammatic view olf he reinforcement of a portion ofthe door s a Referring to Fig. 1 of the drawin s the arrangement of barsin-a typical pane of a flat slab floor supported on y'columns is shown,as though all the concrete in the slab above the upper layers of barswere removed, thus exposing these layers of bars in full while thelayers of bars in the lower art of the slab are indicated by dotted mes.

The reinforce consists of two series of principal tension bars 11, 12,arranged4 at right angles to each other parallel to the rowsof columns.These bars for approximately 4the middle three-fifths of the span areplaced in the lower portion of the slab and are bent up at the ends tolie in the top port-ion thereof, the end portions of the bars extendingoverinto the marginal portions of the adjacent panels, and overlappingthe end port-ions of the similar bars 19, 20 in the adjacent panels.Alternating 'with ythese principal tension bars and grouped ,in tensionacross the middle part oit' the span, and in compression at their ends.rllhe bars 18, la terminate near the margins of each panel, where theyaline with similar bars 5,22 in adjacent panels.

'Each group of bars is width with the width of the the rows of columnsand t provide all the rein bottom of the coextensive in anels betweenetwo oups orce necessary in the slab, as whatever the direction ofthestress in the slab at any given point, it may be resolved into twocomponent stresses, parallel with the reinforcing bars. As the stressesat right angles to the lines connecting adjacent .columns are found tobe less in flat slab loors in the regions remote from the columns thanin the regions near the columns, the lateral spacing of theV th bars lineach group may be graduated, and

the intervals .between the bars `may be greater toward the center of thespan without impairing the strength of the floor.

Heretofore fiat slab floors have been constructed having reinforcingrods crossing the panels diagonally from corner to corner or radiatingfrom the columns through the slab in every direction. Such arrangementsof reinforcin rods do not reinforce the top portions of t e licor slabin the regions bea() .tween adjacent columns against tension stressestransverse to the straight lines connecting said columns. By arrangingthe reinforcing bars in groups parallel to of some of the bars of eachgroup to lie in the top portion of the slab in the marginal -regions ofthe panels in directions `perpendicular to the respective sides thereof,vthereby these bent up bars assist in taking care of the tensionstresses in the top oit' the slab in the regions between the columns.Moreover, in flat slab floors the maximum stress in the slab underordinary conditions of distribution of the load on the Hoor is over thecolumns. Heretofore belts of`reinforcingv bars have been placed crossingeach the' large tensiony stresses This piling up ,of layers of metalover the columns results in lowering the center of gravity of thereinforce and raising the position of the neutral axis oi? the slab,thereby greatly increasing the compression 5; stresses in the lowerportion of the slab in Vthe regions near the columns.

By placing straight bars''in the lower portion of the slab in t-hemarginal regions of the panels and near the columns the so effect of thebent up bars in changing the position of the neutral axis of the slab inthese regions is partly equalized, and at the same time the compressionstresses are distributed between the concrete and straight bars in sucha way as to stiften the slab at 'and compression, in the slab.

at these points.

incoar? the columnsl and reduce the dedection of the slab between thecolumns, thus changn ing the distribution of stresses, both tensionAlso, by arranging the bars in two directions only, the reinforcementover the supports above and below the neutral axis of the Vslab will bein two layers instead of tour or more,V giving the reinforcement a ygreater lever arm for resisting the bending moment at the supports, asthe center of gravity of the reinforcement is farther from the neutralaxis of the slab.

Short supplementary bars 17, 18, are

placed in the upper region of the slabs over and between adjacentcolumns, these bars being perpendicular to the lines connecting ecolumns and disposed at intervals in the planes of the bent up ends ofthe tension bars extending in the same spacing apart of these bars isincreased toward the middle ofthe span, for the same reason as .thespacing apart of the bent up slab bars already referred to. 'llh'e bentup slab bars and the supplementary bars together furnish a sufiicientamount of top reinforcement in this region.

The net work or grillage of top bars may be held in place by main barsl5, 16, two for each row of columns, disposed in the top er, portion ofthe slabparallel to the rows of columns and wired to verticalreinforcing bars in they columns, which latter are not shown in thedrawings. By bending down the ends of the alternate top supplementarybars over the columns, additional shear prcvision can be obtainedlwherever this may' be desirable. By placing these supplementarystraight or bent bars between the main tension bars in the 'upper regionor' the slab over and between the'columns at grada" atedy intervals forthe greater part of' they span, not only is the whole regiony of tensionin the top of the slab between the columns reinforced, but also the barsare so disposed as to be properly proportioned to the varying amount ofthe tensional stresses at various distances from the columns.-

The concrete slab'is increased in thickness over the column for adistance varying from one-third to one-quarter of 'the span. This isdone to decrease the shearing stress' adja- Y cent to the column, and todecrease the' com pressive stress in the concrete on the under side ofthe slab, and results in 'considerable economy of material, as Vatwenty-five per cent.y increase in thickness over this area requires nomore material than an increase in thickness over the total area of theslab of not more than three or four per cent., whereas the increase instrength of the slab as a whole is over twenty-tive per cent.. by reasonof this increased thickness of the slab near t-he columns.

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-ligz 2 shows my improved arrangement l() l direction.; The 35 v oneseries being arranged to ,extend parallel l tom region of`the the topregion-of the sla appliedto a floor slab having one'edge supported in awall, and differs from the arrangement shown in Fig. 1 in omitting thesup lementary tension rods and some of the com ined tension andcompression rods along the edge of the slab supported in the wall.l

While my system or arrangement of metal reinforce is particularlyadapted to floor panels supported atl their corners, it is evident thatit is not restricted thereto, but may be applied to iioor anelssupported on walls at one or more e ges. 4

Having described my improved floor system what I desire to claim andsecure by Letters Patent is as follows:

1. A monolithic floor-slab resting on rows of 'columns intermediate itsmargins and consisting of concrete and series of reinforcing rodspositioned therein, the rods of with a row of ,columns and disposed latgraduated intervals throughout the width of said slab,v and the rods ofanother series being arranged at right anglesto the rods of said firstmentioned series and disposed at graduated intervals throughout thelength of said slab, the rods of both said series spanning the panelsbetween said rows of columns and being bent. to extend through thebottom region of the slab atA the middle portions of the panels andthrough the top region of the slab at the margins of the panels.

2. In a reinforced concrete floor, a floor panel having reinforcing rodsarranged parallel with the respective edges thereof andextendingbeyond-said. edges into the adjacentlpanels respectively, said rodsintersect ingl at right angles toeachother throughout the entire areaofthe panel, and supplementary reinforcing rodsarranged around .theedges of the panel and at right angles thereto, said supplementary rodsbeing in the same horizontal plane with the adjacent portions of thefirst mentionedrods extending in the same direction, there being notmore than two layers of vrods on the same side of the neutral plane ofthe panel at any one point.

3. In a reinforced'concrete floor construe tion consisting of agirderless flat plate slab of concrete resting on rows o-f columnsdividing it into panels along the center lines of said rows, reinforcingbars embedded in said slab arranged in groups of parallel rods, therebeing two groups in each panel, said groups crossing each other and thebars in each group being parallel to a side of the panel and bein spacedapart at intervals from side to si e thereof, the bars of each groupbeing all in the same lane in the botanel `t roughou't their middleportions, an su plementary bars in crossing the edges y of said paneland extending into the adjacent anels, and rods in the to the s abaroundthe margins 0 upon which the supplementary bars rest.

4. In a reinforced-concrete floor construction consist-ing of a slab ofon rows of columns dividing it into along the center lines of -saidrows, reinforcing bars embedded in said slab arranged in groups ofparallel. bars, there being two 'groups in each panel, said groupscrossing eachother, and the bars in'each grou being parallel to a sideof the anelfand eing spaced apart at intervals, ing and being greateratthe middle of the panel than toward the margins,the bars of each groupbeing all in the same plane in the bottom region of' the panelacrossVits middle ortion, some of said bars having their en s offset `upwardlyinto a horizontal plane, and supplementary bars inthe topl region of theslab crossing the edges of said panel and extending into the adjacentpanels, said supplementary bars being in the saine planes with the endsof main bars ex-. tending in the same direction therewith.

5. In a reinforced concrete structure having a pluralit yof panelssupported at the vcorners thereo ,a system of reinforcing rods crossinga panel lin a direction at rightV angles to the line connecting thepoints of support at one edge thereof, and extending. into the adjacentpanels, a second system of reinforcing rods crossing the panel at rightangles to the first mentioned system of rods, and extending into theadjacent'panels, and

bars alternating with these systems of rods -andterminating shortof theedges of the panel.

6. A reinforced ,concrete Hoor panel Vhav-r -ing a pluralityof systemsofparallel ref' inforcing rods arranged to cross each other in adjacentplanes throughout the length region of' the panels concreterestingpanelsl said spacingvaryand breadth of 'said'paneh each of saidsystems comprising straight rods and bent rods .extending inthe samedirection across the panel, the middle portions of' said rods ex-ytending' in the same directionv being ar ranged in the same horizontalplane wyherefv by not 4more than two horizontal layersof rods lie inproximity to each other.

7. A reinforced 'concrete flooring clom-l prising substantiallyrectangular vpanels havin series of reinforcing rods arrange at rig tangles to each other acrossv the length and breadth of a panel parallelwith the respective edges.' thereof, .the ends Vof the rods of eachseries lying inl the saine plane and extendin the ends of thevrods ofeachv series andv parallel' thereto respectively, said-fliers beinto.the V-adjacent. panels, .and barsI positioned inthe plane .of

i'ngarranged in the' marginalre'gion of the v panels and crossing thesame at right angles to their meeting edges;

' 20 into panels defined by -40 and the other` I columns in 8.' Areinforced concrete flooring comprising substantially rectan lar panelshaving Vseries of reinforcing ro s arranged at right angles to eachother across the length and ibreadth of a panel parallel with therespective edges thereof, the ends'of the rods of each series lying inthe same plane and extending into the adjacent panels, andv bars planeof the ends ofpositioned in the the rods of each series and theretorespectively, the bars and rods in the regions adjacent the respectiveedges of p the panels with which they are parallel being spaced nearertogether than ranged across the middle portion of the panels.

9. The combination of columns and a monolithic reinforced concrete floorslab extending across said columns and divided lines passing through thecenters of said columns, ,the reinforcement of each panel comprising aseries of rods extending longitudinally of said' panel and intothepanels contiguous t the ends '25 of said first mentioned panel, and aseparate series of rods extending transversely of said first mentionedpanel and. into thepanels contiguous to the sides of said rst men tionedpanel, the longitudinally extending rods being spaced apart throughoutthe entire width lof the panel, and the transversely extending rodsbeing' s aced apart throughout the entire length or thel anel, all ofsaid rods being in the lower portion of parallel the slab in the middleregion of the panel and some of the rods of each series having theirend' portions offset and lying in the upper part of the slab in theregions adjacent to .the margins ofthe respective lpanels rods of eachseries being straight, whereby said reinforced door slab simulates theaction of a homogeneous flat' plate. 4

l0. A reinforced concrete uniform thickness resting o-n columns arrangedin parallel rows in two directions approximately at right angles to eachother, the lines passing through the centers of the each directiondividing the floor 5,0 into panels, groups of reinforcing kbars in saidslab lying in two directions parallel to the sides of the panels, saidbars being spaced apart at graduated intervals close-r together at themargins of the panels than at their middles, all of the rods of eachgroup being in the lower portion of the slab in the middle region of thepanel and some of said-rods of each group having their end portionsoffset and lying in the upper part of the slab in the regions across themargins of the respective panels, and the other bars of each group beingstraight, whereby said reinforced floor slab simulates the action of ahomogeneous fiat 65. plate.

those ar slab, spaced parallel,

floorv slab of adjacent to and insonne ll. A reinforced concrete doorslab rest'- ing on columns arranged in parallel rows in two directionsangles to each other, the floor slab being of uniform thickness exceptfor the areas adjacent to the columns, where the thickness is increased,reinforcing bars extendin crosswise throughoutthe ength; andv breadt ofsaid slab in two of columns, said `bars being spaced closertogether'near the rows of columns than across the middlesv thereby, some ofthe-'bars in each series being straight, bent bars between saidstraight'bars, said bent bars and straight bars in each series being in the sameplane inthe lower region' of the'slab at theiry middles,

approximately at right series parallel to the rows l" of the panelsdened the ends of` the bent bars in each series extending across themargins of lsaid panels and being 1n a plane-above' said first mentionedplane whereby said reinforced floor slab simulates the action of ahomogeneous flat plate.

12. A reinforcddeconcrete floor slab resting on columns arranged 'inparallel rows in two directions, approximately at right angles to eachother, said slab being of uniform thickness except for the areas adja-Vcent to the columns, said areas being of greater thickness than theremainder of the reinforcing bars in said slab extendinggin twodirections par'- allel to the rows of columns, the spacing apart of thebars beinga minimum near the rows of columns, lsupplemental barsarranged in the slab in the form of grillage in the areas adjacent tothe' columns and- 'means for nsupporting' said supplemental bars in thetop region of the slab whereby said reinforced licor slab simulates theaction of a homogeneous flat plate. l"

13. A reinforced concrete door slab of uniform thickness resting oncolumns arranged iny parallel rows in two directions, the lines plassingthrough the centers of the columns in each direction dividing the floorinto panels,v groups' of parallel reinforcing bars arranged crosswise toeach other, the bars in each of said groups being spaced apart yfromedge to edge of the panels, the spacing of the bars being a maximum inthe middles of the panels and a minimum at the margins of the panels,said groups comprising bent bars passing from below the neutral plane atthe middles of the panels to above'it across the vmargins thereof andstraight bars in the same plane with the middle portions of the bentbars whereby said reinforced floor slab simulates the ac tion of ahomogeneous flat plate.

14. A reinforced concrete floor slab resting on columns arranged in rowsat' right angles to each other, saidslab being of uni-A form thicknessexcept for the areas adjacent to the columns, the thickness of said slabadjacent to the columns being greater than that of the remainder of theslab', reinforcing bars crossing each other at right angles throughoutthe slab, said bars being parallelto the 4rows of columns and spacedapart at graduated intervals, the spacing diminishing from the middlesof the panels toward the rows of columns in each direction, said barspassing from below the neutral plane of the slab at the middles of thepanels to above it across the regions adjacent to the lines connectingthe rows of columns whereby said reinforced floor slab simulates theaction of a homogeneous iiat plate.

15. A reinforced concrete floor slab of uniform thickness resting" oncolumns ar.

ranged in intersecting parallel rows, the lines passing through thecenters of the columns of the rows in each direction dividing the oorinto panels, main reinforcing bars parallel to the sides of said panelspassing from below the neutral plane at the middles of the panels toabove it across the margins thereof and intersecting throughout theslab, said bars being closer together at the margins of the panels thanat the middles thereof, supplemental` bars in the form of grillageplaced in the slab in the areas over and adjacent to said columns, saidsupplemental bars being in the same planes asthe main bars adjacentthereto which extend in the same directionwhereby said reinforced floorslab simulates the action of a homogeneous flat plate.

Signed at St. Louis, Missouri, this 11th day of April, 1911..

A. E. LINDAU. Witnesses:

A. M. HoLooMBE, M. A. SHELTON.

copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. C.

